In this Oct. 15, 2008, file photo, then-Democratic presidential candidate Sen. Barack Obama, D-Ill., left, and Republican presidential candidate Sen. John McCain, R-Ariz., right, exchange responses as debate moderator Bob Schieffer listens during a presidential debate at Hofstra University in Hempstead, N.Y. Finally, the fall season delivers the matchup Americans have been waiting for, President Barack Obama goes one-on-one with Republican Mitt Romney in three prime-time debates. With the race a dead heat, the debates take on an oversized role in the few weeks between now and Election Day. One small mistake or impression - a glance at a watch, repetitive sighing - could roil the campaign for days and linger in voters' mind. This is especially true for two polished candidates who will have the soundbites and rhetoric down cool. By Ron Edmonds, AP file photo

FILE - In these Sept. 26, 2012, file photo, President Barack Obama and Republican presidential candidate Mitt Romney campaign in the battleground state of Ohio. Fierce and determined competitors, Obama and Romney each have a specific mission for the string of three debates that starts Wednesday night, Oct. 3, 2012. Obama, no longer the fresh face of 2008, must convince skeptical Americans that he can do in a second term what he couldn't in his first: restore the U.S. economy to full health. Romney, anxious to keep the race from slipping away, needs to instill confidence that he is a credible and trusted alternative to the president, with a better plan for strengthening the fragile economy. (AP Photos)

Chart shows trend in attitude about whether presidential debates are helpful in deciding which candidate to vote for; second chart shows how much of the 2008 debates people watched. MCT 2012

With CAMPAIGN-DEBATE, McClatchy Washington Bureau by Lesley Clark and David Lightman

WASHINGTON — With his fortunes in several battleground states fading, Mitt Romney will step onto the stage Wednesday night to debate President Barack Obama in what could be one of his last opportunities to change the dynamics of the 2012 election.

The debate in Denver will be the first of three between the two men and could be decisive, particularly for Romney, who has Republicans worried that his campaign is faltering.

“If he doesn’t get on board soon, there’s trouble out there,” said David Woodard, a South Carolina-based Republican consultant. The stakes for Romney, he said, “keep going up with each passing day.”

The debate comes as the Romney campaign desperately tries to reverse weeks of bad headlines and gloomy poll numbers. Obama has built a national lead and a growing edge in key swing states, notably crucial Florida, Ohio and Virginia.

“Romney’s trailing in the critical battleground states, and this is about the last opportunity for a challenger to level the playing field and pick up a bit of momentum,” said Lee Miringoff, director of the Marist Institute for Public Opinion.

Debates do matter: 67 percent of those who voted in 2008 said the debates were helpful in deciding between the candidates, according to the Pew Research Center. But this year’s electorate is unusually polarized, and Miringoff said there appear to be fewer undecided and “persuadables” left to convince at this stage of the election.

“Debates have tended to be reinforcing,” he said. “If you like what the Republicans say you’re going to like what Romney says, and if you like the Democrats you’ll like Obama.”

The race is far from out of reach, of course. Republicans still see hope. The economy, though rebounding slightly, remains sluggish. Unemployment is still over 8 percent, and the Arab world is newly turbulent.

But time is running out for Romney.

“He has to shape the race in the final 40-plus days,” said Craig Robinson, editor of The Iowa Republican newsletter and the former executive director of the Iowa Republican Party. “He needs to focus on showing the differences between himself and the president, and these debates allow him to go on offense.”

Though analysts say debates are rarely game changers, they can elevate a challenger, simply by appearing on the same stage as the incumbent. White House insiders say the first debate is Romney’s best opportunity, because it will be the first time he appears before the nation on an equal footing with the president.

A few of the presidential face-offs have proved pivotal, including the 1960 matchup in which a telegenic John F. Kennedy bested an ailing Richard Nixon and won the White House. In 1980, the debate was held a week before the election, and voters saw and liked an upbeat Ronald Reagan and turned against a gloomy Jimmy Carter. Reagan surged and won the election.

Romney has dismissed talk that his campaign needs a major reset and says it’s picking up steam.

“People acknowledge the last couple of weeks have been challenging,” said campaign adviser Brian Jones. “At the same time, the campaign is getting back into a rhythm, back on track.”

The 90-minute debate at the University of Denver, starting at 9 p.m., will focus on domestic issues. Jim Lehrer, the host of PBS’ “NewsHour,” will moderate.

A second debate on Oct. 16 in New York will use a town hall-style and will feature questions on foreign and domestic policy from the audience. The participants will be undecided voters selected by the Gallup Organization. The third debate on Oct. 22 in Florida will cover foreign policy.

The two vice presidential candidates - Vice President Joe Biden and Rep. Paul Ryan of Wisconsin, the Republican nominee — will debate in Kentucky on Oct. 11.

This year’s debates begin after some battleground states already have started voting. Early voting began in Iowa on Thursday, absentee voting is under way in Virginia, and Ohio voters can begin voting on Oct. 2.

Early preparation

Debates are often judged as much on style as substance, and both campaigns are seeking to temper expectations, falling over each other to paint their candidate as a rusty orator and their opponent as a polished debater. Both sides are working hard to lower expectations for their own candidate.

Romney “has been preparing earlier and with more focus than any presidential candidate in modern history,” said Obama spokeswoman Jen Psaki. She contends Obama will have time to “review and practice” before the debates, but that between “world events, governing” and campaigning, he has had less prep time than the campaign anticipated.

Yet Obama has clearly practiced, slipping off to Democratic National Committee headquarters in Washington to engage with Sen. John Kerry of Massachusetts, a veteran presidential debater who is standing in for Romney. Obama will spend three days next week in Nevada, campaigning and preparing for the debate.

The Romney campaign, in turn, casts the candidate as unaccustomed to one-on-one contests and notes that he’s not debated a Democrat since 2002. By most accounts, he turned in a forceful performance then against Democratic gubernatorial candidate Shannon O’Brien, going on to defeat her to become governor of Massachusetts.

In a memo, Romney senior adviser Beth Myers suggests Romney will be up against “one of the most talented political communicators in modern history.”

The bar is likely higher for Obama. A Suffolk University/NBC12 poll in Virginia — which showed the president with a slim lead over Romney - found that 46 percent of respondents said Obama is the better debater. Just 19 percent selected Romney.

“Barack Obama comes into the debate phase of the election with very high expectations, which may be difficult to meet or exceed,” said poll director David Paleologos. “A credible performance by Romney could shake up the presidential race in Virginia and elsewhere.”